The content described in this part only provides background information of the present embodiment and is not constituted to the prior art.
The wireless communication device refers to devices for sending and receiving data, wherein the data are sent and received by using wireless communication with a managing device such as a server or relaying for the managing device and a wireless communication. The wireless communication device includes not only devices for a purpose of wireless communication such as a tablet PC, a personal computer (PC), a smartphone, or a mobile communication terminal, but also devices of the Internet of Things (IoT) such as smart home appliances, smart watches, and the like. The repeater periodically transmits a beacon, so as to notify an existence of a wireless network, such that the wireless communication device may join the wireless network, and terminals may use the wireless network to send and receive data by receiving the beacon.
Now, in a case that the wireless communication device is an IoT device, the communication session will be continuously held, and a large amount of data will be continuously transmitted and received. Therefore, a problem of power consumption is generated. Such problem related to power consumption does not have a significant impact on devices such as refrigerators, TVs (Televisions), and the like belong the IoT that receives power through common power supplies and devices such as automobiles and the like that have a large-capacity power supply. However, devices such as locks of a door and intelligent watches that may be operated by small batteries and are sensitive to power consumption, thereby having a low power mode in order to minimize power consumption. FIG. 1 shows a method of operating a wireless communication device in low power modes.
FIGS. 1A, 1B, and 1C are diagrams illustrating a method of operating a conventional wireless communication device in low power modes.
FIG. 1A is a graph showing an operation of the wireless communication device in the low power modes.
Wireless communication devices periodically repeat an operation divided into a sleep mode 110 and a wake-up mode 120. The sleep mode is a mode for supplying power only to at least one established of a plurality of constituent elements for enabling wireless communication devices to hold communication sessions and cutting off power to rest of the constituent elements, such that only the minimum of the constituent elements in the wireless communication device operates. In order to that wireless communication devices may operate in the sleep mode and may operate in the wake-up mode again, the wireless communication devices may supply power only to general purpose input/outputs (GPIOs), a timer, and a storage circuit, and may cut off power to rest of the constituent elements to minimize the power consumption, wherein the general purpose input/outputs may receive a clock from outside, the timer may receive a clock signal and provide a moment for changing the modes, and the storage circuit is configured to hold the communication sessions. The wake-up mode is a mode for supplying power to all of the constituent elements in the wireless communication devices, such that all of the constituent elements operate. The wireless communication devices may operate in the wake-up state to receive various data together with a beacon from the repeater for a long time and may operate in the wake-up state to receive the beacon only from the repeater for a short time.
The wireless communication device operates periodically in the sleep mode followed by the wake-up mode according to clock signals received from outside, so that the beacon transmitted by the repeater may be received. The outer clock signals are timed in units of fixed cycles, thereby enabling the wireless communication device to operate in the wake-up mode during a period of the timing. However, in order to change the modes, the clock signals without restrictions such as a standard are received by the wireless communication devices. Therefore, there are problems in which the frequency is lower and the tolerance is very poor. Thus, the problem as shown in FIG. 1B is generated.
FIG. 1B is a diagram showing an embodiment of the conventional wireless communication devices entering the wake-up state.
Conventional wireless communication devices operate in the sleep mode 110 followed by the wake-up mode 120 and then operate in the sleep mode followed by the wake-up mode 140 again, according to the clock signals received from the outside. However, as described above, in order to change the modes, there are problems in which the frequency is lower and the tolerance is very poor. Therefore, it is not possible to align the time in advance of converting from the sleep mode to the wake-up mode in correspondence with a moment 130 at the beacon actually transmitted by the repeater, the conversion of modes will be occurring later. For example, if a tolerance of the clock signal is set to 500 p.p.m. (parts per million) and a cycle of the sleep mode is assumed to be 100 seconds, then the error at the moment of operating in the wake-up mode becomes 0.05 second. Due to such an error, the wireless communication devices operate in the wake-up mode 140 after the moment 130 at the beacon actually transmitted by the repeater, thereby causing a problem in which the beacon or data transmitted by the repeater may not be received.
In order to prevent such a problem, conventional wireless communication devices are controlled as follows, the maximum error at the moment of operating in the wake-up mode is predetermined by referring a cycle of the operation in the sleep mode with the tolerance of a clock signal, and the wake-up mode is operated in advance based on the error. The time in which the wireless communication devices operate in the wake-up mode in advance as described above is referred to as a timing advance (TA: Timing Advance, hereinafter abbreviated as “TA”).
FIG. 1C is a diagram showing another embodiment of the conventional wireless communication devices entering the wake-up state.
The conventional wireless communication devices are controlled to operate in the wake-up mode 145 in advance of a TA 150 that is compared with the moment of operating in the wake-up mode 140 according to the timing of the clock signal. However, in order to prevent a problem of the conventional wireless communication devices operated in the wake-up mode slowly than the moment of the repeater actually transmitting a beacon, the TA is set based on the maximum error at the moment of operating in the wake-up mode, so as to increase the time for the operation in the wake-up mode, thereby generating a problem of increasing the power consumption of the wireless communication device.
Therefore, in order to minimize the power consumption in the wireless communication devices, it is necessary to set the optimal TA.